1. Field of the Invention
The present invention provides methods of improving the flow properties of dry particulate cementitious or non-cementitious materials whereby the materials can be readily conveyed out of storage tanks and the like.
2. Description of the Prior Art
Cementitious materials such as hydraulic cements, slag, and fly ash and non-cementitious materials such as barite, bentonite and fumed silica having various particle size distributions are often dry-blended and placed in storage tanks. The storage tanks containing the cementitious and non-cementitious materials are also often transported by land or sea to locations where the materials are to be used. During such transportation, the materials are subjected to vibrations and as a result, the materials are tightly packed under static conditions. One or more of the materials are often of ultra-fine particle sizes, i.e., sizes in the range of from about 5 to about 100 microns, which causes the tightly packed problem to be more severe. When the cementitious or non-cementitious materials are conveyed out of the storage tanks at the locations of use, significant portions of the tightly packed materials are often left in the storage tanks. The incomplete conveying of the materials results in costs for disposing of the materials and increased costs to the person or entity using the materials.
Cementitious and other non-cementitious mineral materials have heretofore been treated to make them more flowable. For example, U.S. Pat. No. 2,857,286 issued to Striker on Oct. 21, 1958 discloses a process of treating Portland cement with acetic acid or a water soluble salt of acetic acid whereby the Portland cement becomes more flowable. In accordance with the Striker patent, the treatment of Portland cement with the acid or acetate is carried out either concurrently with, or subsequent to, the grinding of the cement clinker. The acid or acetate can be combined with the cement during grinding or the ground cement can be treated by injecting the acid or acetate into the cement under pressure as a vapor in order to blow the cement and uniformly contact it with the acid or acetate.
U.S. Pat. No. 3,094,425 issued to Adams et al. on Jun. 18, 1963 discloses that most cements and similar materials compacted by vibration become semi-rigid and will not flow without considerable mechanical effort to break up the compaction. This condition is known as xe2x80x9cpack set.xe2x80x9d Further, it is stated that it is known that certain polar molecules when added to ground cement will attach to the particles and reduce their surface forces. In accordance with the Adams patent, a mixture of calcium acetate and lignin sulfonate is an effective grinding aid and a pack set inhibitor when interground with a cement or other similar material.
U.S. Pat. No. 3,615,785 issued to Moorer et al. on Feb. 2, 1968 discloses a cement grinding aid and pack set inhibitor comprised of polyol and a water soluble salt of an aliphatic acid having no more than 3 carbon atoms.
The above described additives are difficult to handle and must be added to the cement prior to or after grinding. Since commercially available cementitious and non-cementitious materials generally do not include such additives, they must be provided, handled and combined with the cementitious or non-cementitious materials by the user by spraying, mechanical mixing or other time consuming procedure.
Thus, there are continuing needs for improved methods of enhancing the flow properties of dry cementitious and non-cementitious particulate materials which are stored and/or transported in storage tanks.
The present invention provides improved methods of enhancing the flow properties of a dry particulate cementitious or non-cementitious material or a blend of such materials which meet the needs described above and overcome the deficiencies of the prior art. The methods basically comprise dry-blending a particulate flow enhancing additive comprised of a particulate solid adsorbent material having a flow inducing chemical adsorbed thereon with a cementitious or non-cementitious material prior to placing the material in a storage tank.
The particulate flow enhancing additive of this invention is easily handled, readily dry blended with cementitious or non-cementitious materials and enhances the flow properties of the materials. The presence of the flow enhancing additive in the cementitious or non-cementitious materials allows the materials to be mechanically or pneumatically conveyed out of storage tanks, even when they are tightly packed therein, without leaving significant portions of the materials in the storage tanks.
A preferred particulate flow enhancing additive useful in accordance with this invention is comprised of precipitated silica powder having a flow inducing chemical comprised of glacial acetic acid adsorbed thereon. The weight ratio of precipitated silica powder to the glacial acetic acid in the flow enhancing additive is in the range of from about 90:10 to about 10:90, and the additive is blended with cementitious or non-cementitious materials in an amount in the range of from about 0.01% to about 1.0% by weight of the cementitious or non-cementitious materials.
It has also been discovered that after dry-blending a cementitious or non-cementitious material such as barite with the flow enhancing additive of this invention and placing the resulting blend in a storage tank, if the tank is closed to the atmosphere and the blend is aged in the closed storage tank for a time period in the range of from about one half day to about four days, the particulate blend is more readily and easily conveyed out of the storage tank.
It is, therefore, a general object of the present invention to provide improved methods of enhancing the flow properties of dry particulate cementitious and non-cementitious materials.
Other and further objects, features and advantages of the present invention will be readily apparent to those skilled in the art upon a reading of the description of preferred embodiments which follows.
The present invention provides methods of improving the flow properties of one or more dry particulate cementitious or non-cementitious materials. Examples of the cementitious materials include, but are not limited to, hydraulic cements, slag, fly ash and mixtures thereof. Examples of non-cementitious materials include, but are not limited to, barite, bentonite and fumed silica.
The methods of this invention are particularly suitable for improving the flow properties of a dry particulate cementitious or non-cementitious material or a blend of such materials which are of fine or ultra-fine particle size and are tightly packed under static conditions in a storage tank from which they must be conveyed. This invention also provides methods of storing one or more dry particulate cementitious or non-cementitious materials in a storage tank, transporting the storage tank and cementitious or non-cementitious materials therein to a location of use and then conveying the cementitious or non-cementitious materials out of the storage tank without unintentionally leaving a significant portion of the cementitious or non-cementitious materials in the storage tank. The term xe2x80x9csignificant portionxe2x80x9d is used herein to mean a portion of the stored cementitious or non-cementitious material that is above about 15% thereof by volume.
The methods of this invention are basically comprised of dry-blending a particulate flow enhancing additive comprised of a particulate solid adsorbent material having a flow inducing chemical adsorbed thereon with at least one particulate cementitious or non-cementitious material. Thereafter, the blend of the cementitious or non-cementitious material and flow enhancing additive can be placed in a storage tank and readily conveyed therefrom, either mechanically or pneumatically, without leaving a significant portion of the cementitious or non-cementitious material in the storage tank.
It has also been discovered that after dry-blending a cementitious or non-cementitious material such as barite with the flow enhancing additive of this invention and placing the resulting blend in a storage tank, if the tank is closed to the atmosphere and the blend is aged in the closed storage tank for a time period in the range of from about one half a day to about four days, the particulate blend is more readily and easily conveyed out of the storage tank.
A variety of particulate solid adsorbent materials can be utilized for forming the flow enhancing additive of this invention. Examples of such adsorbent materials include, but are not limited to, precipitated silica, zeolite, talcum, diatomaceous earth and fuller""s earth. Of these, precipitated silica is presently preferred. The adsorbent material utilized must be capable of adsorbing the flow inducing chemical utilized, and remain as a free flowing powder.
The flow inducing chemical utilized in accordance with this invention can be any of the heretofore known chemicals which produce polar molecules that react with particulate materials and increase their flow properties. Examples of polar molecule producing chemicals which can be utilized include, but are not limited to, organic acids such as alkyl and/or alkene carboxylic acids and sulfonic acids, salts of the foregoing acids formed with weak bases and acid anhydrides such as sulfur dioxide, carbon dioxide, sulfur trioxide, nitrogen oxides and similar compounds. The most preferred flow including chemical for use in accordance with this invention is glacial acetic acid. While the exact cause for the flow enhancement of particulate cementitious or non-cementitious materials when contacted with a flow inducing chemical of this invention is presently unknown, it is believed that polar molecules of the chemical react with components of the cementitious or non-cementitious materials such as tricalcium silicate to produce a particle repulsion effect in the materials.
The weight ratio of the particulate solid adsorbent material utilized to the flow inducing chemical utilized in the flow enhancing additive is generally in the range of from about 90:10 to about 10:90, more preferably from about 75:25 to about 25:75. The resulting particulate flow enhancing additive is dry-blended with at least one particulate cementitious or non-cementitious material, the flow properties of which are to be improved, in an amount in the range of from about 0.01% to about 1.0% by weight of the cementitious or non-cementitious material, more preferably in an amount in the range of from about 0.02% to about 0.5%.
A method of the present invention for improving the flow properties of at least one dry particulate cementitious or non-cementitious material is comprised of dry-blending a particulate flow enhancing additive with the cementitious or non-cementitious material, the additive being comprised of a particulate solid adsorbent material having a flow inducing polar molecule producing chemical adsorbed thereon.
Another method of the present invention for improving the flow properties of at least one dry particulate cementitious or non-cementitious material is comprised of dry-blending a particulate flow enhancing additive with the cementitious or non-cementitious material in an amount in the range of from about 0.01% to about 1.0% by weight of the cementitious or non-cementitious material, the additive being comprised of a particulate solid adsorbent material having a flow inducing chemical adsorbed thereon selected from the group of polar molecule producing organic acids, their salts and acid anhydrides.
Yet another method of the present invention for improving the flow properties of at least one dry particulate cementitious or non-cementitious material is comprised of dry-blending with the cementitious or non-cementitious material a particulate flow enhancing additive comprised of a particulate solid adsorbent material selected from the group of precipitated silica, zeolite and talcum having a flow inducing chemical adsorbed thereon selected from the group of polar molecule producing organic acids, their salts and acid anhydrides, the weight ratio of the solid adsorbent material to the flow inducing chemical being in the range of from about 90:10 to about 10:90 and the flow enhancing additive being blended with the cementitious or non-cementitious material in an amount in the range of from about 0.01% to about 1.0% by weight of the cementitious or non-cementitious material.
Still another method of this invention for improving the flow properties of at least one dry particulate cementitious or non-cementitious material is comprised of dry-blending a particulate flow enhancing additive with the cementitious or non-cementitious material, the additive being comprised of precipitated silica powder having a flow inducing chemical comprised of glacial acetic acid adsorbed thereon, the weight ratio of precipitated silica powder to glacial acetic acid being in the range of from about 75:25 to about 25:75 and the flow enhancing additive being blended with the cementitious or non-cementitious material in an amount in the range of from about 0.02% to about 0.5% by weight of the cementitious or non-cementitious material.
A method of this invention for placing at least one dry particulate cementitious or non-cementitious material in a storage tank, transporting the storage tank and cementitious or non-cementitious material to a location of use and then conveying the cementitious or non-cementitious material out of the storage tank without unintentionally leaving a significant portion of the cementitious or non-cementitious material in the storage tank is comprised of dry-blending a particulate flow enhancing additive with the cementitious or non-cementitious material prior to placing the material in the storage tank and then placing the resultant blend of additive and cementitious or non-cementitious material in the storage tank, the additive being comprised of a particulate solid adsorbent material having a flow inducing polar molecule producing chemical adsorbed thereon; preferably a flow inducing polar molecule producing chemical selected from the group of organic acids, their salts and acid anhydrides.
Another method of this invention for placing at least one dry particulate cementitious or non-cementitious material in a storage tank, transporting the storage tank and cementitious or non-cementitious material to a location of use and then conveying the cementitious or non-cementitious material out of the storage tank without unintentionally leaving a significant portion of the cementitious or non-cementitious material in the storage tank is comprised of prior to placing the cementitious or non-cementitious material in the storage tank, dry-blending with the cementitious or non-cementitious material a particulate flow enhancing additive and then placing the resultant blend of additive and cementitious or non-cementitious material in the storage tank, the additive being comprised of a particulate solid adsorbent material selected from the group of precipitated silica, zeolite and talcum having a flow inducing polar molecule producing chemical adsorbed thereon selected from the group of organic acids, salts thereof and acid anhydrides, the weight ratio of the solid adsorbent material to the flow inducing chemical being in the range of from about 90:10 to about 10:90 and the flow enhancing additive being blended with the cementitious or non-cementitious material in an amount in the range of from about 0.01% to about 1.0% by weight of the cementitious or non-cementitious material.
Yet another method of this invention for placing at least one particulate cementitious or non-cementitious material in a storage tank, transporting the storage tank and cementitious or non-cementitious material to a location of use and then conveying the cementitious or non-cementitious material out of the storage tank without unintentionally leaving a significant portion of the cementitious or non-cementitious material in the storage tank is comprised of: (a) dry-blending a particulate flow enhancing additive with the cementitious or non-cementitious material prior to placing the cementitious or non-cementitious material in the storage tank and (b) placing the resultant blend of additive and cementitious or non-cementitious material in the storage tank; the additive being comprised of precipitated silica powder having a flow inducing additive comprised of glacial acetic acid adsorbed thereon, the weight ratio of precipitated silica powder to glacial acetic acid being in the range of from about 75:25 to about 25:75 and the flow enhancing additive being blended with the cementitious or non-cementitious material in an amount in the range of from about 0.02% to about 0.5% by weight of the cementitious or non-cementitious material.
Still another method of placing at least one dry particulate cementitious or non-cementitious material in a storage tank, transporting the storage tank and cementitious or non-cementitious material to a location of use and then conveying the cementitious or non-cementitious material out of the storage tank without unintentionally leaving a significant portion of the cementitious or non-cementitious material in the storage tank is comprised of: (a) dry blending a particulate flow enhancing additive with the cementitious or non-cementitious material prior to placing the cementitious or non-cementitious material in the storage tank; (b) placing the resulting blend of additive and cementitious or non-cementitious material in the storage tank; (c) closing the storage tank to the atmosphere; (d) aging the blend of additive and cementitious or non-cementitious material in the closed storage tank for a time period in the range of from about one half a day to about 4 days; (e) opening the storage tank; and (f) conveying the blend of additive and cementitious or non-cementitious material out of the storage tank; the additive being comprised of precipitated silica powder having glacial acetic acid adsorbed thereon.
In order to further illustrate the methods of the present invention, the following examples are given.